Measuring resilience with fluctuations in body weight

Animal resilience means that animals can cope with changes in the environment. Resilience is important for an animal: to maintain its health, an animal must be able to cope with temporary environmental changes, such as diseases. Animals with higher resilience are less affected by these environmental changes. As a result, resilient animals show fewer fluctuations in production, such as growth/body weight. Genetic improvement of resilience is therefore essential for the livestock industry of the future.

Fluctuations in body weight

To investigate the possibility of genetically improving resilience, the researchers collected monthly body weights from laying hens from four to thirty-two weeks old. A resilience indicator was based on fluctuations in deviations from the measured body weight of a chicken compared to the average of her flock. “In many studies, body weight is only measured at one moment in life, for example at the time of slaughter. In this study, we collected several body weight measurements during the life of a chicken and we looked at their deviations", says researcher Tom Berghof. "We found that chickens differ genetically in their deviations in body weight, which means that we can breed chickens with smaller deviations in body weight and better resilience."

Improving resilience

To investigate whether chickens with genetic differences in resilience also had differences in disease resistance, the researchers investigated two chicken lines with a known difference in immunity and disease resistance. The researchers expected that chickens with a better immune system would have better resilience: animals that cope better with diseases show fewer and smaller fluctuations. Surprisingly, the results showed no indication of a link between resilience and immunity. The absence of this link might be due to the fact that the chicken lines were housed in the WUR research facility, which is a relatively clean environment. Berghof: “You will not see any disease-induced body weight deviations without the presence of a disease.”

“Therefore, to investigate the relation between resilience and disease resistance, we also looked at a different chicken population with an E. coli-infection.” Berghof continues: “We found that chickens with a better genetic predisposition for resilience were less ill than chickens with a poorer genetic predisposition for resilience. So we did find indications that breeding for resilience based on body weight deviations can also lead to improved disease resistance, although not as strong as we initially expected."

Application

The findings of this study can lead to the development of resilience indicators based on body weight measurement, not only for layer chickens, but for all livestock species, like pigs, broilers, and turkeys. In combination with the current technological development on massive data collection (‘big data’), the outlook for application of this study’s findings is promising. Currently, the researcher of Wageningen University & Research and Hendrix Genetics are further optimizing the use of big data to establish solid and reliable resilience indicators for breeding purposes, which will ultimately lead to better animal health and welfare.